Structural safety assessment procedure of plastic single-span greenhouses considering semi-rigid clamp joints

This study evaluated the structural safety of 9 greenhouse types under extreme weather loads using a nonlinear finite element method (FEM) model that accounts for material nonlinearity of clamp joint. Clamp joints were modeled as interface elements representing elastoplasticity, with stiffness and limit strength estimated through loading tests. The FEM model assessed the structural safety of the greenhouses based on allowable stress design criteria, including combined stress. Loading test on two types of clamp joints revealed that SP (Steel-plate) joints exhibited more than twice the limit strength of SW (Steel-wire) joints. This result highlights the potential structural vulnerability of low-cost greenhouses constructed exclusively with SW joints. The nonlinear finite element method (FEM) results identified side rafter pipes as the most vulnerable members due to excessive stress redistributed from semi-rigid joints, while the columns were found to contribute minimally to structural performance. FS values were consistently lower under snow loads than wind loads, with nonlinear FEM showing an average FS reduction of 7.8 % and 4.7 % compared to linear FEM, respectively. Among design parameters, rafter pipe diameter had the greatest impact on FS, while purlin count had minimal influence. These results emphasize the necessity of considering semi-rigid joint behavior in greenhouse design to ensure structural safety under extreme weather conditions. The reliable nonlinear FEM framework developed in this study provides valuable insights for designing safer greenhouses and evaluating existing ones.